From what CityPay understand, there is no known instance-to-instance concerns of the previous CVEs listed. This means that an untrusted neighbour on the physical hardware could not read the memory of another instance or the AWS hypervisor. Amazon state

All instances across the Amazon EC2 fleet are protected from all known instance-to-instance concerns of the CVEs previously listed. Instance-to-instance concerns assume an untrusted neighbor instance could read the memory of another instance or the AWS hypervisor. This issue has been addressed for AWS hypervisors, and no instance can read the memory of another instance, nor can any instance read AWS hypervisor memory. We have not observed meaningful performance impact for the overwhelming majority of EC2 workloads.